From Tenebrae
Diggers (also known as stonebeasts) are notoriously near-sighted though even-tempered, which is not too surprising given they were bred by the khazad. Physically, they resemble their ancient forebearers save for their size, and their front legs are shorter and squatter, made more for slow and steady movement than attacking. When they grow in size, their forearms gain the strength for burrowing.
During war, the digger's jaws may be used to great effect. Their ferocious bite is made all the more deadly when the near-sighted beast is guided by a competent warrior, and many of the most prized are outfitted with even adamantine, which never slows their sturdy, though slow, builds.
Similar to a pony, a khazad may ride even a medium-sized digger, though the more advanced versions are prized as a working and fighting breed. A khazad may invest a considerable amount in his digger mount, crafting expensive, heavy armors as these do not slow the creature...or during war, the creature's inevitable advance.
Digger Companions
Starting Statistics: Size Medium; AC +4 natural armor; Speed 30 ft.; Attack savage bite (1d8); Ability Scores Str 14, Dex 14, Con 15, Int 2, Wis 13, Cha 5; Special Qualities near-sighted (-2 perception checks), darkvision, lowlight vision, slow and steady, Kinship of Stone
4th-Level Advancement: Size Large; AC +3 natural armor; Burrow 10ft.; Attack savage bite (1d10); Ability Scores Str +6, Dex –2, Con +4
Savage Bite (Ex)
A digger's bite is particularly dangerous. It applies 1-1/2 times its Strength modifier to damage inflicted with its bite attack, and threatens a critical hit on a 19–20.
Slow and Steady
Diggers have a base speed of 30 feet, but their speed is never modified by armor or encumbrance.
Kinship of Stone
Over time, the khazad may have introduced earth elementals into the bloodline of this breed. While mounted, the rider may be considered to be "grounded" or "touching earth" for the purposes of specific feats or effects if this is considered beneficial.